Aromatic polymers of 2-bromo-8-hydroxy-5,5-dioxodibenzothiophen

ABSTRACT

NEW AROMATIC POLYMERS COMPRISING UNITS OF THE FORMULA   -O-(5,5-DI(O=)DIBENZOTHIOPHEN-8,2-YLENE)-   AND COPOLYMERS COMPRISING SUCH UNITS AND OTHER UNITS SUCH AS   -O-(1,4-PHENYLENE)-SO2-(1,4-PHENYLENE)-   ARE OF HIGHER SOFTENING POINT THAN POLYMERS OF THE LATTER UNITS ALONE. THE NEW POLYMERS MAY BE MADE USING AN ALKALI METAL SALT OF 2-BROMO-8-HYDROXY-5,5-DIOXODIBENZOTHIOPHEN AS MONOMER OR BY REACTING 2,8-DIBROMO-5,5DIOXODIBENZOTHIOPHEN WITH AN EQUIVALENT AMOUNT OF AN ALKALI METAL HYDROXIDE OR A DI-(ALKALI METAL) SALT OF A BISPHENOL.

Nov. 27, 1973 J, LESUE ET AL 3,775,368

, 5 DTOXODIBENZOTHIOFHEN AROMATIC POLYMERS OF Z-BROMO8 HYDROXY-S FiledJan. 31, 1972 REACTION TIME (MINUTES) US. Cl. 260-49 4 Claims ABSTRACTOF THE DISCLOSURE New aromatic polymers comprising units of the formulaso, and copolymers comprising such units and other units such as are ofhigher softening point than polymers of the latter units alone. The newpolymers may be made using an alkali metal salt of2-bromo-8-hydroxy-5,5-dioxodibenzothiophen as monomer or by reacting2,8-dibromo-5,5- dioxodibenzothiophen with an equivalent amount of analkali metal hydroxide or a di-(alkali metal) salt of a bisphenol.

This application is a continuation-in-part of our application 56,405filed on Lluly 20, 1970, now abandoned.

This invention relates to new aromatic polymers and to new chemicalintermediates from which they may be produced.

In the specifications of British Pats. 1,153,035, 1,153,-

528 and 1,234,301, the disclosures of which are incorporated herein byreference, there are described methods for the production of aromaticpolymers in which a dihalobenzenoid compound having each halogen atomactivated by an electron-attracting group is caused to react with asubstantially equivalent amount of an alkali metal hydroxide. Asexplained in British Pat. 1,153,035, the halogen atoms in thedihalogenobenzenoid compound are preferably chlorine or fluorine. Thefluorine derivatives generally are more reactive and enable thedisplacement of alkali metal halide to be carried out more quickly, butare more expensive. Bromine derivatives are also relatively expensiveand although they resemble the chlorine derivatives in performance, theywould seem to offer no advantages. Iodine derivatives are generally lesssuitable.

Any dihalogenobenzenoid compound or mixture of dihalogenobenzenoidcompounds is suitable, provided the two halogen atoms are linked tobenzene rings which have an electron-attracting group, preferably orthoor para to the halogen atom. The dihalogenobenzenoid compound can havethe halogen atoms linked to the same benzenoid ring or to differentbenzenoid rings, so long as each is activated by an electron-attractinggroup.

Any electron-attracting group inert under the conditions of the reactioncan be used as the activating group in these compounds. The morepowerful electron-attracting groups give the highest reaction rates andare therefore preferred. Electron-donating groups should be absentUnited States Patent 0 "ice from the same benzenoid ring as the halogen.It may be a univalent group that activates one or more halogen atoms inthe same ring, for example a nitro, phenylsulphonyl, alkylsulphonyl,cyano, trifluoromethyl or nitroso group, or heteronitrogen as inpyridine; or it may be a bivalent group that can activate halogen atomsin two different rings, for example a sulphone, sulphoxide, azo,carbonyl, vinylene, vinylidene, tetrafluoroethylene or organic phosphineoxide group; or it may be a bivalent group that can activate halogenatoms on the same ring, as in the case of difiuorobenzoquinone and 1,4-,1,5- or 1,8-difiuoroanthraquinone.

In particular, the dihalogenobenzenoid compound may have the formula inwhich X and X are conveniently the same but may be different and arehalogen atoms, and Y is SO 40- or CO or a radical of the formula inwhich Y and Y" may be the same or different and each is SO -SO or CO andA is a bivalent organic radical, which may be aliphatic, aromatic orheterocyclic and has both valencies linked to carbon atoms. For example,A may be a bivalent aromatic radical derived from benzene, a fused-ringaromatic hydrocarbon containing not more than two aromatic rings (forexample naphthalene, indene, fluorene or dibenzofuran), or a compound ofthe formula in which Z is a direct link, -O, S-, SO CO, a bivalenthydrocarbon or substituted hydrocarbon radical (e.g. alkylene,alkylidene or a bivalent oycloaliphatic or aromatic radical), or aresidue of an organic diol (i.e. the bivalent radical obtained byremoving the hydrogen atoms from the two hydroxy groups). The halogenatoms in the dihalogenobenzenoid compounds are preferably in the paraposition to the bridging group Y, because the essentially all-parapolymers that can be made from them have better physical properties asthermoplastic materials.

Lower alkyl, alkoxy or alkylthio groups may be present as substituentson any of the aromatic rings but are preferably absent from thehalogen-bearing rings and are also preferably absent altogether when thearomatic polymer is required to be stable at high temperatures.

The dihalobenzenoid compound may, in particular, have the formulaX-Q-SOz-A-SOzQ-X' I in British specification 1,177,183 (the disclosureof which Patented Nov. 27, 1973 of aromatic polymers whose molecularchains comprise units of the formula in which an alkali metal salt of ahalophenol of the formula (Where X is halogen) is polymerised by thedisplacement of alkali metal halide.

British specification 1,177,183 describes polymers having recurringunits of the formula OE in which E is the residuum of a halophenol, i.e.the bivalent aromatic residue of the compound after removal of thehalgen atom and aromatic hydroxyl group from the halophenol. Anyhalophenol may be used provided that the halogen atom is bonded to abenzene ring having an electron-attracting group in at least one of thepositions ortho or para to the halogen atom. The halophenol can beeither mononuclear where the halogen atom and hydroxyl group areattached to the same benzene ring or polynuclear where they are attachedto different benzene rings, provided that there is the electronattracting group in the ortho or para position of the benzene ringcontaining the halogen atom.

Any electron-attracting group can be employed as the activator group inthe halophenols. It should be, of course inert to the reaction, butotherwise its structure is not critical. Preferred are the strongactivating groups for example the sulphone group (-SO bonding twobenzene rings as in 4-(4-chlorophenyl-sulphonyl)phenol and4-(4-fluorophenylsulphonyl) phenol, although such other strongattracting groups hereinafter mentioned can also be used.

The more powerful of the electron-attracting groups give the fastestreactions and hence are preferred. It is further preferred that the ringcontains no electron supplying groups on the same benzene ring as thehalogen; however, the presence of other groups on the ring or in theresiduum of the halophenol can be tolerated. Preferably, all of thesubstituents on the halophenol residuum are either hydrogen (zeroelectron-attracting), or other groups having a positive sigma* value, asset forth in J. F. Bunnett in Chem. Rev., 49, 273 (1951) and Quart.rev., 12, 1 (1958).

The electron-attracting group of the halophenol compound can functioneither through the resonance of the aromatic ring, as indicated by thosegroups having a high sigma* value, i.e. above about +0.7 or by inductionas in perfluoro compounds and other electron sinks.

Preferably, the activating group should have a high sigma* value,preferably above 1.0, although suflicient activity to promote thereaction is evidenced in those groups having a sigma* value above 0.7,although the reaction rate with such a low powered electron-attractinggroup may be somewhat low.

The activitating group can be basically either of two types:

(a) Monovalent groups that activate displacement of a halogen on thesame ring as the aromatic hydroxy group for example a nitro group,phenylsulphone, phenylcarbonyl, alkylsulphone, cyano, trifluoromethyl,nitroso and hetero nitrogen as in pyridine,

(b) Divalent groups that activate displacement of a halogen on a ringjoined by the divalent group to a ring having the aromatic hydroxylgroup, for example the sulphone group --'-SO the carbonyl group C0; thevinyl group CH=CH-; the sulphoxide group SO; the azo-group N=N-; thesaturated fluorocarbon groups -CF CF organic phosphine oxides EPO(R)},where R" is a hydrocarbon and the ethylidene group {(XCXZH were X can behydrogen or halogen, or divalent groups which can activate a halogen onthe 4 same ring as the aromatic hydroxyl group for exampledifiuorobenzoquinone, 1,4- or 1,5- or 1,8-difluoroanthraquinone.

If desired, the polymers may be made with mixtures of two or morehalophenols having substantially the same reactivities which may havedifferent or the same electron-attracting groupsrThus the E residuum ofthe halophenols in the polymer structure may be the same or different.

In British specifications 1,078,234 and 1,133,561 (the disclosures ofwhich are included hereinby reference), there is disclosed a method forthe production of aromatic polymers having recurring units of theformula (where X is halogen, preferably chlorine or fluorine) and thedihydric phenol may in particular he one of the following:

A QtQ- A no-Q-smQ-on (where the A group represents hydrogen, loweralkyl, lower aryl and the halogen-substituted groups thereof).

According to the present invention there are provided new aromaticpolymers whose molecular chains comprise units of the formula ll Ueither alone or copolymerised with other units, and with units of theformula RE and/or units of the formula R--E'R--E in which formulae R isoxygen or sulphur and E, E and E are as defined above, in particularunits of the formula Polymers containing a substantial proportion ofunits of the former formula (e.g 10 of the former units for of thelatter in the polymer) are of higher softening point than equivalentpolymers having units of thevlatter formula alone, and a usefulmodification of theproperties of the latter polymer maybe obtained bythe presence of as little as 1 of the former units for 99 of the latter,in the polymer. Polymers containing units of the former formula are ofhigher softening point than equavalent polymers having units of thelatter formula alone.

According to the invention there are also provided as new chemicalintermediates 2-bromo-8-hydroxy-5,5-

dioxodibenzothiophen and the alkali metal salts thereof.

Of these compounds, 2-bromo-8-hydroxy-5,5-dioxodi benzothiophen,possessing a reactive bromine atom as well as a phenolic group,can.serve as a valuable chemical. intermediate for producing a varietyofproducts; for example the bromine atom canbe replaced by .amino andsubstituted amino groups or by oxygenor sulphurcontaining anions toproduce amines, ethersandsulphides.

The alkali metal salts of thisbromophenol can be polymerised to give thenew polymers of the invention.

This bromophenol and its alkali metal salts may be prepared by theaction of alkali metal hydroxide on .2,8- dibromo 5,5dioxodibenzothiophen in a manner similar to that described for thehalfway hydrolysis of bis-(4- chlorophenyl) sulphone in Britishspecification 1,153,035. The alkali metal salt of the bromophenol isinitially obtained dissolved in the reaction medium and is preferablyused directly, although for the purpose of purification it may be moreconvenient in some cases to acidity and then isolate the freebromophenol. This can be converted back into an alkali metal salt bytreatment with a suitable base (e.g., an alkali metal hydroxide oralkoxide). The alkali metal is conveniently potassium or sodium.Displacement of alkali metal halide often occurs more readily if thepotassium cation is present in the reagent used, but the weight (andusually the price) per mole of a potassium compound is higher than forthe corresponding sodium compound. Some or all of the alkali metalcation in the reagent may be replaced by an organic onium cation havinga positively charged heteroatom (for example a quaternary ammoniumcation such as tetramethyl ammonium) stable under the conditions of thereaction, and the term alkali metal salt as used herein is deemed torefer also to salts containing such onium cations.

Further according to the invention, there is provided a method formaking new aromatic polymers having units of the formula in which analkali metal salt of 2-bromo-8-hydroxy-5,5- dioxodibenzothiophen, or amixture of 2,8-dibromo- 5,5-dioxodibenzothiophen and an equivalentamount of an alkali metal hydroxide or of the di-(alkali metal) salt ofa dihydric phenol is polymerised at ISO-400 C. by the displacement ofalkali metal halide. These reagents may be polymerised alone, or theymay be copolymerised with alkali metal salts of other activatedhalophenols (or with mixtures of activated dihalobenzenoid compounds andan equivalent amount of alkali metal hydroxide), in particular thosedescribed in British specifications 1,153,035 and 1,177,183; or they maybe copolymerised with mixtures of di-(alkali metal) salts of dihydricphenols and activated dihalobenzenoid compounds as described in Britishspecifications 1,078,234 and 1,133,561. The halogen atoms in thehalophenol or dihalobenzenoid compound are activated byelectron-attracting groups such as I SO 'ortho or para to the halogenatom. The comonomer may for example be an alkali metal salt of a 4-(4halophenylsulphonyl)phenol or a mixture of a bis-(4- halophenyl)sulphone with an equivalent amount of alkali metal hydroxide. Thehalogen atoms in the comonomer are preferably chlorine (for cheapness)or fluorine (for greater reactivity), although the bromide derivativesmay also be used.

In a further embodimnet of the invention, block copolymers may be formedby polymerizing an alkali metal those having repeating units flit)either alone or copolymerised with each other and/or up to of unitshaving the formula where the halogen atoms are preferably chlorine orfluorine. The fluorine derivatives generally are more reactive andenable the displacement of alkali metal halide to be carried out morequickly or at a lower temperature, but are more expensive. Brominederivatives are also relatively expensive and although they resemble thechlorine derivatives in performance they offer no advantages. Iodinederivatives are generally less suitable.

The alkali metal is conveniently potassium or sodium. Displacement ofalkali metal halide often occurs more readily if the potassium cation ispresent in the reagent used, but the weight (and usually the price) permole of a potassium compound is higher than for the corresponding sodiumcompound. Some or all of the alkali metal cation in the reagent may bereplaced by an organic onium cation having a positively chargedhetero-atom (for example a quaternary ammonium cation such astetramethyl-ammonium) stable under the conditions of the reaction, andthe term alkali metal salt as used herein is deemed to refer also tosalts containing such onium cations.

The polymerisation is preferably carried out in a polar liquid which isa solvent for alkali metal phenoxides and is stable under the reactionconditions employed, although an alkali metal salt of2-bromo-8-hydroxy-5,S-dioxodibenzothiophen may also be polymerised orcopolymerised with another alkali metal salt of a halophenol in themelt.

Suitable polar liquids for the reaction include the lower dialkyl andcyclic alkylene sulphoxides and sulphones (e.g. dimethyl sulphoxide and1,1-dioxothiolan, aromatic nitriles (e.g. benzonitrile) and diarylketones (e.g. benzophenone), sulphoxides and sulphones. The total amountof solvent used is desirably sufiicient to ensure that none of thestarting materials is in the solid state in the reaction mixture.

Changing the liquid reaction medium may be convenient as it allows theinitial use of liquids that would be less suitable for the final stages,being for example inconveniently volatile or unstable at polymerizationtemperatures or incapable of dissolving the resultant polymer to thedesired extent. For example, dimethyl sulphoxide is a convenientsolvent, especially for the hydrolysis of2,8-dibromo-5,S-dioxodibenzothiophen with alkali metal hydroxide, but itcannot be used at such high temperatures as 1,1-dioxothiolan (cyclictetramethylene sulphone).

The liquid reaction medium need not contain any solvents for polymer ofhigh molecular weight even at the later stages of the reaction, althoughif it does not the product is of relatively low molecular weight unlessthe final stage of polymerisation is carried out in the melt; this maybe explained if the molecular chains of the polymer cease to grow in thesolid state.

The rate of polymer formation in the reaction of the invention riseswith rise of temperature and below 200 C. is usually uneconomicallyslow. It may, however, be advantageous to preheat the reaction mixturebetween 150 C. and 200 C. and then raise the temperature to produce thepolymer. Temperatures up to 400 C. may be employed, and about 250 C. isusually convenient.

The reaction should initially be carried out under pressure if necessaryto prevent the escape of 2,8-dibromo-5,5- diaxodibenzothiophen or otherdihalobenzoid compound and any volatile solvent or cosolvent. Heating invacuum may however be desirable at a later stage to remove unwantedsolvents, e.g. dimethyl sulphoxide which may decompose at thetemperatures required to produce high polymer.

The vessel used should be made of or lined with a material that is inertto alkali metal phenoxides and also to alkali metal halides under theconditions employed. For example, glass is unsuitable as it tends toreact with phenoxide anions at high temperatures, upsetting thestoichiometry of the polymerisation and contaminating the product withsilicate. Some grades of stainless steel undergo surface crazing atthese temperatures in the presence of alkali metal halide, and vesselsmade of or lined with titanium or nickel or an alloy thereof or somesimilarly inert material are preferable.

The polymerisation may conveniently be carried out in an extruder or ona heated metal hand.

To neutralise any reactive oxygenor sulphur-containing anions, a reagenttherefor may be introduced at the termination of the polymerisation.Reactive monofunctional haldies, for example methyl chloride, areparticularly suitable.

The alkali metal halide can be removed from the resultant high polymerby any suitable means. For example, it can be extracted from the highpolymer using water, or the polymer itself can be dissolved in astrongly polar organic solvent (for example dimethyl formamide,1-methyl-Z-oxopyrrolidine, dimethyl sulphoxide, 1,1-dioxothiolan ornitrobenzene) and then reprecipitated by addition to a liquid such aswater which is miscible with the polymer solvent but itself is anon-solvent for the polymer.

When the polymer is formed in solution, a convenient procedure is to addthe reaction mixture (which may be decanted or filtered from solidalkali metal halide) to an excess of a liquid which is miscible with thereaction solvent but in which the polymer is insoluble. If the reactionsolvent is water-miscible, or is miscible with a liquid in whichresidual alkali metal halide also dissolves, the polymer can thus beobtained in one step. Otherwise, as for example if the reaction mixtureis poured into methanol, the precipitated polymer initially containsalkali metal halide which can subsequently be washed out with water.

The reduced viscosity of the polymers of the invention is desirably atleast 0.3 (measured at 25 C. at 1% w./v. in a solvent such as dimethylformamide) if they are to serve for structural purposes as athermoplastic. In general, the new thermoplastic polymers of thisinvention may be used in any of the ways described for similarthermoplastic aromatic polysulphones in British specification 1,016,245.

* The following examples illustrate the invention.

EXAMPLE v1 A solution of 2,8-dibromo-5,5-dioxodibenzothiophen (3.7408g.; 0.010 mole) and dimethyl sulphoxide (225 cm. was stirred at 1200.10.05 deg. C. in a stainless steel vessel under nitrogen. 1.000 Naqueous potassium hydroxide (40 cmfi; 0.040 mole) (preheated to C.) wasrapidly added to the solution. This technique ensured that thethermostatically controlled temperature was maintained at the same levelduring the mixing period. The system was homogeneous; samples wereremoved periodically and titrated for unused potassium hydroxide,potassium phenates and liberated bromide ion.

The graph on the accompanying drawings shows the amount of bromide ionper mole of 2,8-dibromo-5,5- dioxodibenzothiophen liberated as afunction of time. The facile removal of one bromine atom and the lessready removal of the second bromine atom is an obvious conclusion fromthis graph. The graph also suggests that a small amount of cleavage ofthe ring system has occurred to produce the dipotassium salt of3,3'-dibromo-6-hydroxybiphenyl-6-sulphonic acid, which would not beexpected to liberate bromide ions with base.

EXAMPLE 2 A suspension of 2,8-dibromo-5,S-dioxodibenzothiophen (75 g.;0.202 mole) in dimethyl sulphoxide (500 cm. was heated to C. and to thestirred mixture was added dropwise an aqueous solution of potassiumhydroxide (46.5 cmfi; 0.404 mole). The mixture was vigorously stirredfor 3 hours at 110 C. after the complete addition of the base, thencooled to 50 C. and filtered. The filtrate was poured into water (2litres), and the aqueous solution was acidified with hydrochloric acid.The colourless precipitate which formed was filtered off, washed twicewith water, dried and recrystallised from methanol. The yield was 55 g.and the material melted with decomposition. An analytically pure samplewas obtained by recrystallisation from nitrobenzene and had infra-redand nuclear magnetic resonance spectra which were consistent with8-bromo-2-hydroxy-5,5-dibromodibenzothiophen.

HO Br 8-bromo-2-hydroxy-5,5 dioxodibenzothiophen (10.95 g.) wassuspended in water (10 cm. and a solution of 1 N potassium hydroxide(35.2 cm?) was added. The mixture was warmed and stirred to 60 C.,filtered, and the filtrate was evaporated to dryness to give thepotassium salt as a yellow powder. The salt was dried in a vacuumdesiccator at C. overnight. A

This potasium salt (7 g.) and dimethyl sulphone (10 g.) were heatedtogether under an atmosphere of dry nitrogen at 230 C. for 24 hours. Themixture wasvthen allowed to cool to C. and dimethyl formamide (20 cm?)was added, and the solution was poured into methanol. The precipitatedvpolymer was washed with hot methanol and hot water and finally dried.The polymer had a reduced viscosity of 0.42 (measured at 25 C. on a 1%w./v. solution in dimethyl formamide, i.e. a solution containing 1 g. ofpolymer per 100 cm. of solution), and infra-red and nuclear magneticresonance spectra which were consistent with a polymer having repeatingunits of the structure Copolymers containing these units and units ofthe formula in the ratios 1;1, 1:5 and 1:10 are made by heating togetherthe above potassium salt and the potassium salt of4-(4-chlorophenylsulphonyl)phenol (using 1,5 and 10 molar proportionsrespectively) in 1,1-dioxothiolan as solvent.

What is claimed is:

1. An aromatic polymer having a reduced viscosity of at least 0.3 asmeasured at 25 C. in a solution of the polymer in dimethyl formamidecontaining 1% w./v. polymer and whose molecular chains consistessentially of units of the formula copolymerized with to 99 units, per100 units in the polymer chain, of units selected from the classconsisting of units of the formula and units of the formula-R-E'--R--E-- wherein R is an oxygen or sulphur atom, E is the residuumwhich can be derived by moving a hydroxy and a halogen from a halophenolhaving an electron-attracting group having a sigma* value of at least0.7 in at least one of the positions ortho or para to the halogen atom,E is the residuum which canbe derived by removing two hydroxy groupsfrom a dihydric phenol, and E is the residuum which can be derived byremoval of two halogens from a dihalobenzenoid compound having eachhalogen atom activated by an electron-attracting group having a sigrna*value of at least 0.7.

2. An aromatic polymer according to claim 1 whose molecular chainsconsist essentially of units of the formula 10 copolymerized with O tounits, per units in the polymer chain, of the formulae where the G grouprepresents hydrogen, lower alkyl or lower aryl.

3. An aromatic polymer as set forth in claim 1 whose molecular chainsconsist essentially of units of the formula 4. An aromatic polymer asset forth in claim 1 whose molecular chains consist essentially of unitsof the copolymerized with 0 to 90 units, per 100 units in the polymerchain, of the formula References Cited UNITED STATES PATENTS HAROLD H.ANDERSON, Primary Examiner L. L. LEE, Assistant Examiner US. Cl. X.R.

260-30.2, 30.8 R, 30.8 DS, 23.4, 32.6 R, 329.3, 823

